This invention relates generally to electrical systems of motor vehicles. More particularly, the invention relates to a circuit that prevents battery drain that might otherwise occur after an idling engine has been automatically shut down by an idle shutdown timer.
Certain motor vehicles that have diesel engines for their motors include idle shutdown timers that shut down the motors when the motors have been idling for some specified amount of time. In some vehicles that have electronic engine control systems, the idle shutdown function is embodied by electronics in an electronic module of the control system.
When an individual, such as the driver, is not present at idle shutdown, the switch that turns the engine on and off will remain on. Such a switch is typically key-operated and is commonly referred to as an ignition switch. Even if a person were present at idle shutdown, he or she might not turn the ignition switch off.
The present invention arises through the recognition that after an engine has been automatically shutdown by an idle shutdown timer, certain electric circuits in the vehicle may remain energized through the ignition switch, consuming energy from one or more DC storage batteries in the vehicle electrical system in the process. An ignition switch that remains on after idle shutdown may therefore cause a battery drain, and if the drain continues long enough, insufficient battery power may be available when it is desired to re-start the engine.
The present invention relates to a circuit that is associated with an ignition switch and an electronic module of an engine control system in a motor vehicle to prevent battery drain caused by the ignition switch remaining on after the idling engine has been automatically shutdown by a shutdown timing function performed by the engine control system.
A preferred embodiment of the inventive circuit employs two relays through which the ignition switch feeds various circuits of the vehicle electrical system when the ignition switch is on and the engine is running. When the engine has been running at idle for some specified amount of time, as monitored by the engine control system, an electronic module of the engine control system operates the relays in a way that causes them to interrupt the feeds to the various electrical system circuits, thereby preventing battery draining that would otherwise occur because of failure to turn the ignition switch off.
The invention provides a cost-efficient solution for avoiding battery draining, and the possible inconvenience of having to jump-start the engine, replace one or more batteries, or perhaps even tow the vehicle.
One general aspect of the invention relates to a motor vehicle comprising an engine whose operation is under control of an engine control system that performs an idle shutdown function to shut down the engine via a programmable output of an electronic module of the control system after the engine has been running in idle without interruption for some amount of time. An ignition switch can be operated on and off for signaling the engine control system to turn the engine on and off. Load circuits are fed through the ignition switch when the ignition switch is on. An interface is connected between the ignition switch and the load circuits and to the programmable output of the module for controlling feeding of the load circuits from the ignition switch by allowing the feeding when the ignition switch is on and the programmable output of the module is not signaling an idle shutdown and by disallowing the feeding when the programmable output of the module is signaling an idle shutdown.
According to a disclosed embodiment of the invention, the interface comprises one or more relays.
Another general aspect of the invention relates to a method for preventing battery drain caused by an ignition switch through which load circuits are fed remaining on after an engine that has been idling continuously in a motor vehicle for some amount of time has been automatically shutdown by an idle shutdown timing function performed by an engine control system. The method comprises programming a programmable output of a module of the engine control system to deliver an idle shutdown signal upon the idle shutdown timing function signaling an idle shutdown. The method further comprises connecting an interface between the ignition switch and the load circuits and to the programmable output of the module to control feeding of the load circuits from the ignition switch by allowing the feeding when the ignition switch is on and the programmable output of the module is not signaling an idle shutdown and by disallowing the feeding upon the programmable output signaling an idle shutdown.
According to a disclosed embodiment of the invention, the method interface comprises operating one or more relays from a condition allowing the feeding to a condition disallowing the feeding when idle shutdown is signaled.
The foregoing, along with further aspects, features, and advantages of the invention, will be seen in the following disclosure of a presently preferred embodiment of the invention depicting the best mode contemplated at this time for carrying out the invention. The disclosure includes a drawing, briefly described as follows.